Delta Tau GEO BRICK LV Guide D’Exploitation
Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables
62
Units:
Multiplication factor
Default:
7 (80 MHz)
I52 controls the operational clock frequency of the Turbo PMAC’s CPU by controlling the multiplication
factor of the phase-locked loop (PLL) inside the CPU. The PLL circuit multiplies the input 10 MHz
(actually 9.83 MHz) clock frequency by a factor of (I52 + 1) to create the clock frequency for the CPU.
Formally, this is expressed in the equation:
factor of the phase-locked loop (PLL) inside the CPU. The PLL circuit multiplies the input 10 MHz
(actually 9.83 MHz) clock frequency by a factor of (I52 + 1) to create the clock frequency for the CPU.
Formally, this is expressed in the equation:
CPU Frequency (MHz) = 10 * (I52 + 1)
I52 should usually be set to create the highest CPU frequency for which the CPU is rated. For the
standard 80 MHz CPU, it should be set to 7.
standard 80 MHz CPU, it should be set to 7.
Note:
It may be possible to operate a CPU at a frequency higher than its rated frequency,
particularly at low ambient temperatures. However, safe operation cannot be
guaranteed under these conditions, and any such operation is done entirely at the
user’s own risk.
particularly at low ambient temperatures. However, safe operation cannot be
guaranteed under these conditions, and any such operation is done entirely at the
user’s own risk.
I52 is actually used at power-on/reset only, so to make a change in the CPU frequency with I52, change
the value of I52, store this new value to non-volatile flash memory with the SAVE command, and reset
the card with the $$$ command.
the value of I52, store this new value to non-volatile flash memory with the SAVE command, and reset
the card with the $$$ command.
If too high a value of I52 has been set, the watchdog timer on the Turbo PMAC will likely trip
immediately after reset due to CPU operational failure. If this happens, the Turbo PMAC must be re-
initialized, using E51 on a Turbo PMAC, or E3 on a Turbo PMAC2.
immediately after reset due to CPU operational failure. If this happens, the Turbo PMAC must be re-
initialized, using E51 on a Turbo PMAC, or E3 on a Turbo PMAC2.
I53
Auxiliary Serial Port Baud Rate Control
Range:
0 to 15
Units:
None
Default:
0 (disabled)
I53 controls the baud rate for communications on the Option 9T auxiliary serial port. Turbo PMAC uses
I53 only at power-up/reset to set up the frequency of the clocking circuit for the auxiliary serial port. To
change the baud rate, it is necessary to change the value of I53, store this value to non-volatile flash
memory with the SAVE command, and reset the card. At this time, Turbo PMAC will establish the new
baud rate.
I53 only at power-up/reset to set up the frequency of the clocking circuit for the auxiliary serial port. To
change the baud rate, it is necessary to change the value of I53, store this value to non-volatile flash
memory with the SAVE command, and reset the card. At this time, Turbo PMAC will establish the new
baud rate.
The possible settings of I53 and the baud rates they define are:
I53
Baud Rate
I53
Baud Rate
0
Disabled
8
9600
1
600
9
14,400
2
1200
10
19,200
3
1800
11
28,800
4
2400
12
38,400
5
3600
13
57,600
6
4800
14
76,800
7
7200
15
115,200
If the optional auxiliary serial port is not present on a Turbo PMAC, or if it is not being used, it is best to
set I53 to 0 to disable the port, so that the computational overhead will not continually checking the port.
set I53 to 0 to disable the port, so that the computational overhead will not continually checking the port.
Baud rates set by odd values of I53 are not exact unless the CPU is running at an exact multiple of 30
MHz (I52 = 2, 5, 8, 11, 14, 17, 20, 23). For most of these baud rates, the errors are small enough not to
matter. However, for 115,200 baud, the CPU must be running at an exact multiple of 30 MHz to
establish serial communications.
MHz (I52 = 2, 5, 8, 11, 14, 17, 20, 23). For most of these baud rates, the errors are small enough not to
matter. However, for 115,200 baud, the CPU must be running at an exact multiple of 30 MHz to
establish serial communications.